Several studies have shown a positive effect of commitment making on behavior change. For instance, burn and Oskamp (1986) carried out a commitment intervention that was aimed at household recycling. Participants in the commitment conditions were approached by a boy Scout who asked them to sign a pledge card. If they signed the pledge, the scout handed them a sticker to post in their home to remind them to recycle. It is not clear how many participants actually signed the card. Results of this study showed a significant difference between the commitment condition and the control group in frequency of recycling during the pledge period; no long-term follow-up data were collected. No additional constructs were measured in this study and it is thus not clear which underlying psychological process was influenced by this manipulation of commitment.
In another neighbourhood recycling study, participants were randomly assigned to one of four conditions for introducing a new curb side pickup program (flyer only; telephone and flyer; face to face and flyer; and written commitment and flyer; werner et al., 1995). Four parallel streets were included in the study, and all residents on a street were assigned to the same condition (total n= 309). Results indicated that a signature commitment was sig- nificantly more effective at inducing regular recycling than the other three conditions. This difference was most pronounced during the first 3 months of the 4-month program.
C ha pt er 5 72 72
Table 5.1 Summary of environmental studies using a commitment manipulation
Commitment Effective: Short Term
(Treatment in Place) Commitment Effective: Longer Term (Treatment Ended)
Author, date Dependent variables Commitment manipulation Commitment only Commitment Plus Commitment only Commitment Plus
Burns & Oskamp (1986) Household recycling (all materials;
city program)
Boy Scout project; asked resident to sign pledge card; provided reminder sticker in both Commitment conditions
C-only vs. ctrl, p< .05 a) C+persuasive message vs. ctrl, p < .05 b) C+persuasive message vs. C-only, n.s. c) C+persuasive message vs. persuasive message only, n.s.
Werner et al., 1995 Household recycling Signed commitment versus information
via flyer, telephone, or face to face Signed commitment most effective for repeated recycling, p < .05
Signed commitment most effective for 3 of 4 months
Pardini &
Katzev (1983-84) Newspaper recycling Weak commitment: Face to face verbal commitment; Strong commitment: Face to face signed commitment
Both weak and strong commitment more successful than information only
Weeks 3 & 4: Strong commitment group maintained recycling; weak commitment group did not.
Wang & Katzev (1990) Experiment 1
Paper recycling Retirement home ABA design; Group meeting; signed group commitment
Commitment vs.
baseline, p< .003 4-wk follow-up C-group vs. baseline, p< .004
Katzev & Pardini
(1987-88) Newspaper recycling Undergraduate experimenter; resident signed form making a 5-week recycling commitment; both experimenter and resident kept copy of form
Frequency C-only vs. ctrl, p < .01 Weight C-only vs. ctrl, p < .001 Frequency a) C+token vs. ctrl, p < .01 b) C+token vs. C-Only, n.s. c) C+token vs. token only,
n.s. Weight
a) C+token vs. ctrl, p < .02 b) C+token vs. C-Only, n.s. c) C+token vs. token only,
n.s. 3-week follow-up: Frequency C-only vs. ctrl, n.s. Weight C-only vs. ctrl, n.s. 3-week follow-up: Frequency a) C+token vs. ctrl, p < .05 b) C+token vs. C-Only, n.s. c) C+token vs. token only, p < .01 Weight
a) C+token vs. ctrl, n.s b) C+token vs. C-Only, n.s. c) C+token vs. token only, n.s. DeLeon & Fuqua (1995) Recycling Mailed request. P signed form and
mailed back; names to be published in newsletter; 55 % (C only) and 75 % (C+) committed; data presented for all.
C-only vs. ctrl, n.s. a) C + group feedback, p < .02; increase due only to those who committed) Matthies et al. (2006) Use of alternative
transportation (bus, metro, bike, etc.)
Personal request; Written; public to research team; all committed, but only 38/191 participants chose to commit to transit No ME for C-only predicting DV (phase 2 or 3, p > .10) a) C + free ticket (phase 2 or 3, p > .10) b) C by personal norm interaction (phase 3, p < .03)
Week 25 Follow-up: No ME for C-only predicting DV Week 25 Follow-up: C by personal norm interaction, p < .08
Cobern et al. (1995) Grass cycling Personal request. Signed card to grass cycle for 4 weeks; public to research team. 70 % in C-only agreed; 80 % in C+ agreed; data presented for all.
C-only vs. ctrl, n.s. a) C + agent (block leader) vs. ctrl, p < .05 b) C + agent (block leader)
vs. C-only, p < .05
Immediate Follow-up: C-only v. ctrl, n.s. 1-year Follow-up: Returned to baseline
Immediate Follow-up: a) C+ Block Leader v. ctrl, p < .05 b) C+ Block Leader v. C-only, p < .05 1-year Follow-up: Returned to baseline
A Review of Commitment Making Strategies in Environmental Research 73
A Review of Commitment Making Strategies in Environmental Research 73
Table 5.1 Summary of environmental studies using a commitment manipulation
Commitment Effective: Short Term
(Treatment in Place) Commitment Effective: Longer Term (Treatment Ended)
Author, date Dependent variables Commitment manipulation Commitment only Commitment Plus Commitment only Commitment Plus
Burns & Oskamp (1986) Household recycling (all materials; city program)
Boy Scout project; asked resident to sign pledge card; provided reminder sticker in both Commitment conditions
C-only vs. ctrl, p< .05 a) C+persuasive message vs. ctrl, p < .05 b) C+persuasive message vs. C-only, n.s. c) C+persuasive message vs. persuasive message only, n.s.
Werner et al., 1995 Household recycling Signed commitment versus information
via flyer, telephone, or face to face Signed commitment most effective for repeated recycling, p < .05
Signed commitment most effective for 3 of 4 months
Pardini &
Katzev (1983-84) Newspaper recycling Weak commitment: Face to face verbal commitment; Strong commitment: Face to face signed commitment
Both weak and strong commitment more successful than information only
Weeks 3 & 4: Strong commitment group maintained recycling; weak commitment group did not.
Wang & Katzev (1990) Experiment 1
Paper recycling Retirement home ABA design; Group meeting; signed group commitment
Commitment vs.
baseline, p< .003 4-wk follow-up C-group vs. baseline, p< .004
Katzev & Pardini
(1987-88) Newspaper recycling Undergraduate experimenter; resident signed form making a 5-week recycling commitment; both experimenter and resident kept copy of form
Frequency C-only vs. ctrl, p < .01 Weight C-only vs. ctrl, p < .001 Frequency a) C+token vs. ctrl, p < .01 b) C+token vs. C-Only, n.s. c) C+token vs. token only,
n.s. Weight
a) C+token vs. ctrl, p < .02 b) C+token vs. C-Only, n.s. c) C+token vs. token only,
n.s. 3-week follow-up: Frequency C-only vs. ctrl, n.s. Weight C-only vs. ctrl, n.s. 3-week follow-up: Frequency a) C+token vs. ctrl, p < .05 b) C+token vs. C-Only, n.s. c) C+token vs. token only, p < .01 Weight
a) C+token vs. ctrl, n.s b) C+token vs. C-Only, n.s. c) C+token vs. token only, n.s. DeLeon & Fuqua (1995) Recycling Mailed request. P signed form and
mailed back; names to be published in newsletter; 55 % (C only) and 75 % (C+) committed; data presented for all.
C-only vs. ctrl, n.s. a) C + group feedback, p < .02; increase due only to those who committed) Matthies et al. (2006) Use of alternative
transportation (bus, metro, bike, etc.)
Personal request; Written; public to research team; all committed, but only 38/191 participants chose to commit to transit No ME for C-only predicting DV (phase 2 or 3, p > .10) a) C + free ticket (phase 2 or 3, p > .10) b) C by personal norm interaction (phase 3, p < .03)
Week 25 Follow-up: No ME for C-only predicting DV Week 25 Follow-up: C by personal norm interaction, p < .08
Cobern et al. (1995) Grass cycling Personal request. Signed card to grass cycle for 4 weeks; public to research team. 70 % in C-only agreed; 80 % in C+ agreed; data presented for all.
C-only vs. ctrl, n.s. a) C + agent (block leader) vs. ctrl, p < .05 b) C + agent (block leader)
vs. C-only, p < .05
Immediate Follow-up: C-only v. ctrl, n.s. 1-year Follow-up: Returned to baseline
Immediate Follow-up: a) C+ Block Leader v. ctrl, p < .05 b) C+ Block Leader v. C-only, p < .05 1-year Follow-up: Returned to baseline
C ha pt er 5 74 74
Commitment Effective: Short Term
(Treatment in Place) Commitment Effective: Longer Term (Treatment Ended)
Pallak & Cummings
(1976) Energy conservation (meter reading)
Signed consent form, “C-public” understood names would be in paper as “public spirited fuel-conserving citizens.” Both public and private commitment groups heard 20 mins. information about effectives ways to save energy. Natural gas a) C-public vs. ctrl, p < .05 Electricity a) C-public vs. ctrl, p < .05 Natural gas a) C-public vs. C-private, p < .05 Electricity a) C-public vs. C-private, p < .05
12 month follow-up Natural gas a) C-public vs. ctrl, p < .01 for use period,
winter months only Electricity (central air conditioning) a) C-public vs. ctrl, p < .03, all year Electricity (window air conditioning) a) C-public vs.
ctrl, p < .01, summer only
12 month follow-up
a) C-public vs. C-private, p < .01 for use period, winter months only
Electricity (central air conditioning) a) C-public vs. C-private, p < .03, all year Electricity (window air conditioning) a) C-public vs. C-private, p < .01, summer only Shippee & Gregory
(1982) Energy conservation (meter reading)
Mild commitment: Newspaper ad thanking for conserving, listing names of firms in program.
Strong commitment: Newspaper ad thanking for conserving and listing amount conserved by each firm.
a) C-mild vs. ctrl, p < .03 b) C-strong vs. ctrl, p < .03 c) C-strong vs. C-mild, p < .03, C-mild conserved more Wang & Katzev (1990)
Experiment 2 Paper recycling College dormsGroup commitment: Two group meetings, then signed group form (1 refused).
Individual commit:
One contact, signed individual form (1 refused). DV = Frequency a) C-group vs. ctrl, p< .001 b) C-individual vs. ctrl, p< .001 c) C-individual vs. C-group, p< .05, C-individual higher. DV = Weight a) C-group vs. ctrl, n.s. b) C-individual vs. ctrl, p< .001 c) C-individual vs. C-group (not reported). 4-wk follow-up DV = Frequency a) C-group vs. ctrl, n.s. b) C-individual vs. ctrl, p< .01 c) C-individual vs. C-group, (not reported) DV = Weight
No differences
A Review of Commitment Making Strategies in Environmental Research 75
A Review of Commitment Making Strategies in Environmental Research 75
Commitment Effective: Short Term
(Treatment in Place) Commitment Effective: Longer Term (Treatment Ended)
Pallak & Cummings
(1976) Energy conservation (meter reading)
Signed consent form, “C-public” understood names would be in paper as “public spirited fuel-conserving citizens.” Both public and private commitment groups heard 20 mins. information about effectives ways to save energy. Natural gas a) C-public vs. ctrl, p < .05 Electricity a) C-public vs. ctrl, p < .05 Natural gas a) C-public vs. C-private, p < .05 Electricity a) C-public vs. C-private, p < .05
12 month follow-up Natural gas a) C-public vs. ctrl, p < .01 for use period,
winter months only Electricity (central air conditioning) a) C-public vs. ctrl, p < .03, all year Electricity (window air conditioning) a) C-public vs.
ctrl, p < .01, summer only
12 month follow-up
a) C-public vs. C-private, p < .01 for use period, winter months only
Electricity (central air conditioning) a) C-public vs. C-private, p < .03, all year Electricity (window air conditioning) a) C-public vs. C-private, p < .01, summer only Shippee & Gregory
(1982) Energy conservation (meter reading)
Mild commitment: Newspaper ad thanking for conserving, listing names of firms in program.
Strong commitment: Newspaper ad thanking for conserving and listing amount conserved by each firm.
a) C-mild vs. ctrl, p < .03 b) C-strong vs. ctrl, p < .03 c) C-strong vs. C-mild, p < .03, C-mild conserved more Wang & Katzev (1990)
Experiment 2 Paper recycling College dormsGroup commitment: Two group meetings, then signed group form (1 refused).
Individual commit:
One contact, signed individual form (1 refused). DV = Frequency a) C-group vs. ctrl, p< .001 b) C-individual vs. ctrl, p< .001 c) C-individual vs. C-group, p< .05, C-individual higher. DV = Weight a) C-group vs. ctrl, n.s. b) C-individual vs. ctrl, p< .001 c) C-individual vs. C-group (not reported). 4-wk follow-up DV = Frequency a) C-group vs. ctrl, n.s. b) C-individual vs. ctrl, p< .01 c) C-individual vs. C-group, (not reported) DV = Weight
No differences
C ha pt er 5 76 76
As described in a previous section, people who recycled had the most favourable attitudes at the end of the project, regardless of treatment condition. werner et al. interpreted this to indicate that attitudes had become more favourable and more accessible because of par- ticipation in the program, and discounted the idea that a mindless need for consistency had driven the commitment group to recycle.
Pardini and Katzev (1983-84) studied the effect of strength of commitment on news- paper recycling. Their experiment consisted of three conditions. The first was information, in which participants were informed about the recycling project by means of a leaflet. Second was the minimal commitment condition, in which participants were given the same informa- tion and were asked by the experimenter to verbally commit to recycling in the next two weeks. Finally, in the strong commitment condition, the same procedure was carried out but participants were asked to sign a commitment form.
During the intervention phase, both commitment groups recycled more frequently than the information group; the commitment groups did not differ from each other. During the 2-week follow-up phase, however, recycling frequency in the minimal commitment condi- tion dropped, while recycling frequency in the strong commitment condition remained high. This difference supports Cialdini’s (2001) recommendation that a commitment should be active in order to have long-term effects. Since no additional constructs were measured, it is not possible to identify which psychological process mediated the effect of commitment on recycling.
wang and Katzev (1990, Experiment 1) showed that group commitment is effective in increasing recycling. In their study, residents of a retirement home were first given general information about paper recycling. At a later time, the participants met with the experimenter for a discussion about the importance of recycling which ended with elicitation of a group commitment to recycle. Participants were told that, if the recycling program were to continue, the experimenter needed to know that there were enough interested participants. They were asked to sign a group commitment form that stated “we, the residents of the 2nd floor, are will-
ing to participate in the paper recycling project sponsored by the Reed College Environmental Group. It is understood that any recyclable paper can be placed in the “recycle” garbage can. we commit ourselves to participating in this recycling project for the next 4 weeks.” Of the 22 participants present, 17 signed the consent form. Results showed that after the group com- mitment manipulation, recycling increased by 47 % compared to baseline. During a 4-week follow-up (when participants were no longer bound by their commitment) recycling rates remained high, making this commitment manipulation a successful one. This study differs from other studies reviewed here because of the emphasis on group commitment instead of an individual commitment. It might be that participants in this study experienced a group norm to follow up on their commitments. Unfortunately, no measures of attitudes, self-concepts or group norms were measured, but the nature and success of the manipulation indicates that a group norm might have mediated the effect of commitment.
A Review of Commitment Making Strategies in Environmental Research 77
A Review of Commitment Making Strategies in Environmental Research 77
Katzev and Pardini (1987-88) compared the single and combined effects of token reinforcers (coupons) and commitment making on increasing recycling. Participants in the commit- ment conditions were asked to sign a commitment form. It is not reported whether or not everyone complied with this request. Results of this study showed that during the 5-week intervention phase, all three experimental conditions (commitment, token, and combined commitment and token) yielded increased recycling, without one being more effective than the other. However, during the 3-week follow-up period, recycling remained high in the commitment and combined conditions but decreased significantly in the token condition. The combined intervention was most successful in terms of frequency and weight measures of recycling. The commitment condition was most effective in terms of number of house- holds that recycled at least once. These results are clearly promising since they show that relatively long term effects can be achieved with interventions containing commitments. Again, no additional constructs were measured in this study and it is thus not clear which underlying psychological process was operating in this study.
Summarizing, we have found four studies that show a main effect of a commitment manipulation on pro-environmental behavior. None of these studies include additional psy- chological constructs that could explain this effect and it is thus not possible to draw strong conclusions concerning possible mediators. However, the study done by wang and Katzev (1990, Experiment 1) suggests that a group norm might have been active, causing the effect of commitment making on behavior.